1. Field of the Invention
The present invention relates to dispersions for incorporation with a synthetic fiber-forming polymer and to improved processes for melt-spinning yarn from a fiber-forming polymer. More particularly the present invention relates to dispersions of polymer additives, especially titanium dioxide particles to control fiber luster and dyes to color the yarn, and a carrier of either a fatty acid ester of pentaerythritol or a fatty acid ester of dipentaerythritol.
2. Description of the Prior Art
In spinning highly viscous synthetic polymers such as polyamides and polyesters, it is common to incorporate additives in order to obtain required characteristics of the final polymer for specific end uses. Many such additives are known and utilized to control dyeing, static, luster, flammability, light stability, brightness, etc. A particularly preferred additive is titanium dioxide, used to decrease the luster of the resulting fiber spun from the molten polymer through conventional techniques and equipment such as a filter, spin pot, spinnerette, quench stack and take-up equipment or winder.
These additives can be incorporated in a variety of ways. In a conventional melt-spinning process starting with fiber-forming polymer chips, the additives can be added initially with the monomeric components and mixed during polymerization, or the additives can be used to coat the polymer chips. See, for example, U.S. Pat. No. 3,673,147 to Bor, hereby incorporated by reference. In both the conventional and continuous melt-spinning processes, it should be desirable to add the additives to the process stream at a point where the polymer is molten by continuously injecting a dispersion comprising the additive and a carrier into the polymer melt prior to spinning. In this manner the concentration of additive could readily be varied without a lengthy polymer transition. Further, additive agglomerates generated during polymerization would be eliminated or decreased.
Polybutene has been successfully used as a carrier for injection of organic copper stabilizers for nylon (see U.S. Pat. No. 4,061,708 to Lazarus et al., hereby incorporated by reference) and as a carrier for injection of organic copper stabilizers and titanium dioxide for polyester (see U.S. Pat. No. 4,070,342 to Lazarus et al., hereby incorporated by reference).
Unfortunately, the high temperature and pressure conditions experienced subsequent to injection cause some polybutenes to boil and vaporize; if flashed to the atmosphere, the polybutene could be condensed and collected as a contaminated oil. Also, some polybutenes separate from the pigment when exposed to high polymer melt temperature. In order to avoid this problem, the present invention was developed.
It is believed the closest prior art in U.S. Pat. Nos. 3,833,542 to Lazarus et al.; 3,956,008 to Knepper et al.; 4,061,708 to Lazarus et al.; and 4,070,342 to Lazarus et al.